JP6768378B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus using an electrophotographic method.

Image forming devices such as printers, copiers, and printing devices apply heat and pressure while sandwiching and transporting recording materials that electrostatically carry toner between rotating bodies that are in pressure contact with each other and rotating. It has a fixing device as a fixing unit for melt-fixing the toner on the recording material. As a heating method in such a fixing device, there is a method of using a film, a belt, or the like as a rotating body to heat a part of the inside of the rotating body in the circumferential direction (see Patent Document 1). In this method, the heat capacity of the heating member is small, and the time required to reach the fixing temperature (warm-up time) is short. Therefore, the time (first print time) from the start of printing to the ejection of the first image-formed recording material to the paper ejection section is short.

In the method of heating a part of the rotating body, when the rotating body is heated for a long time with the rotating body stopped, the temperature difference between the heated region and the non-heated region becomes large, so that the heat resistance and durability of the material used for the rotating body become large. There may be sexual problems. Further, when the rotating body is heated in a stopped state and the rotating body is driven immediately before the fixing operation, the temperature unevenness in the circumferential direction may cause the toner to melt unevenly on the recording material. Therefore, in the method of heating a part of the rotating body, in order to shorten the first print time, the fixing device is started to be heated at the same time as the printing operation is started, and the rotating body is started to start.

Further, the second motor, which is the drive source of the rotating body for fixing, may be configured as a drive source different from the first motor, which is the drive source of the photoconductor and the intermediate transfer body. In this configuration, first, only the second motor is driven in order to shorten the first print time. The first motor may not operate unnecessarily until the timing when it is necessary to start image formation.

JP-A-2002-169407

However, in the above fixing device, in order to shorten the first print time, the fixing device is heated and the second motor is started at the same time as the printing operation is started. Naturally, the start timing of the first motor will be started at the same time as or later than the start of the second motor. As a result, the low-voltage power supply, which is the power supply source for the second motor and the first motor, supplies power to the first motor while supplying power to the second motor. Therefore, for the low-voltage power supply, it is necessary to design the power by adding the peak power at the start of the first motor to the drive power of the second motor.

An object of the present invention is to provide a technique capable of reducing the peak electric power for driving a motor and enabling a stable warm-up operation in a fixing portion.

In order to achieve the above object, the image forming apparatus of the present invention
An image forming part that forms a developer image on the recording material,
A fixing part that heats and fixes the developer image on the recording material,
The first motor that drives the image forming unit and
The second motor that drives the fixing part and
A control unit that controls the first motor and the second motor,
In an image forming apparatus equipped with
The second motor is a stepping motor.
The control unit starts the rotation of the second motor at a speed in the self-starting region, suspends the second motor at the timing of starting the first motor, and then causes the second motor in the self-starting region. The rotation is restarted at a speed, and the speed of the second motor is changed to a speed outside the self-starting region before the recording material reaches the fixing portion.

According to the present invention, it is possible to reduce the peak power for driving the motor and enable a stable warm-up operation in the fixing portion.

The figure which shows the image forming apparatus of Example 1 of this invention. The flowchart which shows the drive control method of Example 1 of this invention. Timing chart diagram showing the drive control method according to the first embodiment of the present invention.

Hereinafter, embodiments for carrying out the present invention will be described in detail exemplarily based on examples with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in this embodiment should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions. That is, it is not intended to limit the scope of the present invention to the following embodiments.

[Example 1]
Examples of the image forming apparatus to which the present invention can be applied include various image forming apparatus using an electrophotographic method such as a printer, a copying machine, and a printing apparatus. The image forming apparatus according to the embodiment of the present invention is an intermediate transfer belt type color laser beam printer.

The configuration and operation of the image forming apparatus of this embodiment will be described with reference to FIG. The color laser beam printer 201 (hereinafter referred to as printer 201), which is the image forming apparatus of this embodiment, superimposes images of four colors (Y: yellow, M: magenta, C: cyan, Bk: black) to form a color image. A four-color image forming unit is provided for forming the image. When the printer 201 receives the image data signal 203 from the host computer 202, the print image generation unit 204 in the printer 201 expands the image data 203 into desired video signal format data to generate a video signal 205 for image formation. .. The generated video signal 205 is transmitted from the print image generation unit 204 to the control unit 206.

The control unit 206 has a CPU 209, a memory, and the like as a control unit that performs arithmetic processing and operation control of each unit of the device. The control unit 206 that has received the video signal 205 irradiates the drum-shaped electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) with image exposure by the image exposure means 3. The photosensitive drums are four-color photosensitive drums 1y, 1m, 1c, and 1k, and are rotationally driven by the first motor 101 at a predetermined peripheral speed (process speed). The first motor 101 is controlled by the first motor ON signal 251 so as to reach a target peripheral speed. The first motor 101 is composed of a brush motor or a brushless motor that performs feedback control so as to reach a target speed.

The photosensitive drums 1y, 1m, 1c, and 1k are rotated, and the charging rollers 2y, 2m, 2c, 2
It is uniformly charged with a predetermined polarity and potential by k, and then receives image exposures 3y, 3m, 3c, and 3k by the image exposure means 3. As a result, an electrostatic latent image corresponding to the color component image of the target color image is formed. The electrostatic latent image is then developed at the developing position by the developers 4y, 4m, 4c, 4k and visualized as a toner image.

The intermediate transfer belt 10 is a non-terminating belt, and is stretched by tensioning members (drive roller 11, tension roller 12, auxiliary roller 18). The intermediate transfer belt 10 has a contact portion that comes into contact with the photosensitive drums 1y to 1k, and is rotationally driven by the rotation of the drive roller 11 at a peripheral speed substantially the same as that of the photosensitive drums 1y to 1k. The toner image formed on the photosensitive drums 1y to 1k is applied to the primary transfer rollers 14y, 14m, 14c, and 14k in the process of passing through the contact portion between the photosensitive drums 1y to 1k and the intermediate transfer belt 10. It is transferred onto the intermediate transfer belt 10 by the voltage (primary transfer).

The toner image as the four-color developer image on the intermediate transfer belt 10 is applied to the secondary transfer roller 20 in the process of passing through the secondary transfer nip between the intermediate transfer belt 10 and the secondary transfer roller 20. By the transfer voltage, it is collectively transferred to the surface of the recording material P (secondary transfer). The recording material P is fed from the paper cassette 52 by the paper feed roller 50. When the paper feed electromagnetic clutch 51 is turned on, the paper feed roller 50 transmits the rotation of the first motor 101 to rotate, and the paper feed operation of the recording material P is performed. The paper-fed recording material P reaches the resist roller pair 54, and the registration sensor 53 is turned on. At this time, in order to align the toner image formed on the intermediate transfer belt 10 with the paper fed by the paper feed roller 50, the paper feed electromagnetic clutch that connects the first motor 101 and the paper feed roller 50 is connected. Turn 51 ON / OFF. The rotation of these series of drive parts is performed by using the first motor 101 as a drive source. As described above, the configuration until the four-color toner image is supported and formed (unfixed) on the recording material P corresponds to the image forming portion in the present invention.

After that, the recording material P carrying the four-color toner image is introduced into the fixing device 30 as a fixing portion, and the four-color toner is melt-mixed and fixed to the recording material P by heating and pressurizing there. Toner. By the above operation, a full-color printed image is formed.

Next, the operation of the fixing device 30 will be described in detail. The fixing device 30 has a basic configuration of a heating roller 32 and a pressure welding roller pair of the fixing roller 31 (pressurizing roller). The heating roller 32 is made of a cylindrical film material, and a heater 34 is inserted and arranged inside the heating roller 32 as a heat source. The temperature of the heater 34 is controlled by controlling the energization of the heater 34 by the heater energization signal 240 so that the outer peripheral surface is maintained at a predetermined fixing temperature. The film of the heating roller 32 is configured to slide with the heater 34 in contact with the inner surface. On the other hand, since the fixing roller 31 that comes into contact with the outer surface is configured to be driven, it rotates in conjunction with the rotation of the fixing roller 31.

At the time of toner fixing, the recording material P on which the unfixed toner image to be image-fixed is formed and supported by the fixing nip portion which is the mutual pressure contact portion of the roller pair is introduced and sandwiched and conveyed, and the heat of the heating roller 32 is fixed. The unfixed toner image is thermally and pressure-fixed to the recording material P by the pressing force of the nip portion. Further, the fixing roller 31 is rotated by using a stepping motor (second motor) 33 that can rotate at a pulse rate in a self-starting region (for example, 0 to 600 pps (pulses per second) depending on the specifications of the motor) as a drive source. The self-starting region of the stepping motor 33 as used herein is a frequency region in which the stepping motor 33 can be started and stopped instantly in synchronization with a pulse signal input from the outside and can rotate forward and reverse. Shows general basic characteristics.

The low-voltage power supply 230 is the power source of the first motor 101, the second motor 33 which is the drive source of the fixing device 30, and the heater 34 described above, and adjusts the power supplied from the commercial power source outside the device. Supply to each part. Each motor or the like is powered by a low voltage power supply 230.

<Drive control method at the start of printing>
The drive control at the start of printing in the present invention will be described with reference to the flowchart of FIG. First, the host computer 202 transmits the image data signal 203 to the print image generation unit 204 <T301>. Next, the print image generation unit 204 transmits the video signal 205 to the control unit 206 and starts counting the timer 1 <T302>. The control unit 206 transmits an ON signal of the heater energization signal 240 <T303>. Next, <T304> starts the self-starting rotation (for example, 300 pps) of the second motor.

The control unit 206 starts counting the timer 1 from the reception of the video signal, and stops the second motor 33 <T306> after the elapse of the predetermined time T2 <T305>. Next, in order to perform image drawing, the first motor ON signal 251 is transmitted <T307>. The recording material P is set to T2 hours so that the heating roller 31 reaches the fixing device 30 after reaching a temperature at which the heating roller 31 can be sufficiently fixed. In this T2 time, the time from the start of driving the first motor 101 to the time when the recording material P reaches the fixing device 30 is subtracted from the time from when the heater is energized to when the temperature reaches the heater temperature which can be fixed. It will be time. For this T2 time, a value that is changed according to the paper type is stored in advance in the control unit 206 (memory).

The control unit 206 starts counting the timer 2 together with <T307> for transmitting the first motor ON signal <T308>. Next, the control unit 206 determines whether or not the first motor 101 has reached the target speed based on the speed stabilization signal generated through the feedback control of the first motor 101 <T309>. When the control unit 206 receives the speed stabilization signal of the first motor 101, the second motor 33 restarts the self-starting rotation <T310>.

In the paper feeding operation of the recording material P, after the first motor speed ON signal is transmitted <T307>, the paper feeding roller 50 rotates in conjunction with the ON of the paper feeding electromagnetic clutch 51, and the paper feeding operation is started. The control unit 206 counts T4 with the timer 2 for a shorter time than when the recording material P reaches the fixing device 30 after starting the driving of the first motor 101 <T312>. After the timer 2 counts T4 hours, the control unit 206 switches the speed of the second motor 33 (for example, 300 pps → 1000 pps) <T315>. The speed is increased or decreased by increasing or decreasing the clock frequency of the CPU 209.

The control unit 206 starts fixing <T316> after switching the speed of the second motor 33 <T315>. The fixing speed is set to a speed at which the recording material P that passes through the secondary transfer nip and reaches the fixing device 30 can be smoothly conveyed by switching the speed.

Using the timing chart of FIG. 3, the drive current of the low-voltage power supply 230 will be described by the flowchart of FIG. 2 above. The control unit 206 receives the video signal 205 <T302>. Immediately after that, the ON signal of the heater energization signal 240 is transmitted <T303>. <T304> to start the self-starting rotation of the second motor 33. Therefore, a current that rotates the second motor 33 by self-start flows through the low-voltage power supply 230.

Next, the control unit 206 stops the second motor 33 <T306> in order to perform image drawing after the elapse of the predetermined time T2 <T305>. Next, the ON signal 251 of the first motor 101 is transmitted <T307>. Therefore, in the low voltage power supply 230, only the starting current of the first motor 101 flows, and it is possible to avoid that the starting current of the first motor 101 and the current of the second motor 33 are added. Further, since the second motor 33 is driven at a pulse rate (300 pps) within the self-starting region (0 to 600 pps), it can be stopped instantly without requiring a speed fall time.

Next, the control unit 206 determines whether or not the first motor 101 has reached the target speed based on the speed stabilization signal of the first motor 101 <T309>, and then the self-starting rotation (300 pps) of the second motor 33. <T310> to resume. Therefore, since the second motor only needs to be stopped for a short time when the first motor 101 is up, it is possible to avoid temperature unevenness in the circumferential direction of the heating roller 31.

After transmitting the first motor ON signal 251 <T306>, the time T4 is counted <T312>. After the lapse of T4 hours, the speed of the second motor 33 is switched to the fixing speed (1000 pps) <T315>, and fixing is started <T316>.

By using the above control, the maximum drive current value Ip shown in the total current of the low-voltage power supply 230 in FIG. 3 is only the start-up current value of the first motor 101, and the drive current of the second motor 33 is added. You don't have to. Further, since the second motor 33 rotates in the self-starting region, it can be stopped and started instantly in synchronization with the input pulse signal, and the speed rise time is not required. Therefore, the time for starting the second motor at a constant speed is not required, and the stop time of the heating roller 32 can be shortened, so that the adverse effect of temperature unevenness due to the speed unevenness of the heating roller 32 can be avoided.
The warm-up operation of the fixing device 30 may be started before the timing of receiving the image data signal from the host computer. For example, when a print preparation signal is sent from the host computer before the image data signal is transmitted, the rotation of the second motor 33 in the self-starting region may be started at the reception timing of the print preparation signal. Good.

As described above, in the present embodiment, first, the second motor is started to rotate at the speed of the self-starting region, and the second motor is temporarily stopped at the timing of starting the first motor. Then, after the first motor stabilizes at a predetermined speed, the pause of the second motor is released and the rotation at the speed of the self-starting region is restarted. Then, the speed of the second motor is accelerated to a speed outside the self-starting region before the recording material reaches the fixing device. According to this embodiment, in order to shorten the first print time, it is possible to reduce the peak power of the low-voltage power source while starting the fixing device first. Therefore, conventionally, the power at the start of the first motor is added to the drive power of the second motor, but only the peak power of the first motor is required. Further, since the second motor uses the second motor and rotates in the self-starting region of the second motor, the start / stop time can be shortened, and the harmful effect of the fixing temperature unevenness can be avoided.

The pulse rate of the second motor 33 when driving the fixing roller 31 during the warm-up operation and the actual heating fixing operation of the fixing device 30 is not limited to the above. The pulse rate outside the self-starting region during the heating and fixing operation described in this embodiment is, for example, the pulse rate during heating and fixing of plain paper, and for example, in the heating and fixing of thick paper, the pulse rate is within the self-starting region. It may be the value of. Needless to say, even when the pulse rate during the heating and fixing operation does not fall outside the self-starting region, the above-mentioned effects such as reduction of the peak power of the low-voltage power supply can be obtained, but in the present invention, the pulse rate during the heating and fixing operation is A particularly remarkable effect can be obtained when operating outside the self-starting area.

201 ... Printer, 202 ... Host computer, 203 ... Image data signal, 204 ... Printed image generator, 205 ... Video signal, 206 ... Control unit, 209 ... CPU

Claims (7)

An image forming part that forms a developer image on the recording material,
A fixing part that heats and fixes the developer image on the recording material,
The first motor that drives the image forming unit and
The second motor that drives the fixing part and
A control unit that controls the first motor and the second motor,
In an image forming apparatus equipped with
The second motor is a stepping motor.
The control unit starts the rotation of the second motor at a speed in the self-starting region, suspends the second motor at the timing of starting the first motor, and then causes the second motor in the self-starting region. An image forming apparatus comprising restarting rotation at a speed and changing the speed of the second motor to a speed outside the self-starting region before the recording material reaches the fixing portion. The first aspect of the present invention is the first aspect of the present invention, wherein the control unit releases the temporary stop of the second motor and restarts the rotation at the speed of the self-starting region after the first motor stabilizes at a predetermined speed. Image forming device. The image forming apparatus according to claim 1 or 2, wherein when the control unit receives an image data signal from a host computer, the second motor starts rotating at a speed in a self-starting region. Claim 1 or 2 characterized in that, when the control unit receives a print preparation signal sent from the host computer at a timing prior to the image data signal, the control unit starts the rotation of the second motor at a speed in the self-starting region. The image forming apparatus according to. The fixing portion includes a tubular film, a heater in contact with the inner surface of the film, and a rotatable fixing roller in contact with the outer surface of the film, and the second motor is the fixing roller. The developer image formed on the recording material is heat-fixed by the heat of the heater while the recording material is sandwiched and conveyed between the fixing roller and the film by rotating the film.
The image forming apparatus according to any one of claims 1 to 4, wherein the heater continues to heat even while the second motor is temporarily stopped. The image forming apparatus according to any one of claims 1 to 5, wherein the first motor is a brush motor or a brushless motor capable of feedback control. The image forming portion contains at least a photoconductor and contains at least a photoconductor.
The image forming apparatus according to any one of claims 1 to 6, wherein the first motor rotates the photoconductor.

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